Boron containing automotive gear oil

ABSTRACT

The disclosed technology relates to an automotive gear oil, which may be used, for example, in heavy duty manual transmissions and axles, and includes an oil of lubricating viscosity, 1 wt % or less of a dispersant, and at least one boron containing compound.

BACKGROUND OF THE INVENTION

The disclosed technology relates to an automotive gear oil, which may beused, for example, in manual transmissions and axles, and includes anoil of lubricating viscosity, 1 wt % or less of a dispersant, and atleast one boron containing compound. The automotive gear oil isparticularly useful as a single lubricant to lubricate both thetransmission and the axle.

Deposits of decomposition products such as carbon, varnish and sludgecause serious problems in gearboxes. The tendency towards decompositionproducts is particularly strong among synthetic automotive gear oilswhich have long drain intervals. As such, cleanliness is a mandatoryrequirement in automotive gear oils, and particularly modern automotivegear oils based on synthetic base oils.

Most modern automotive gear oils contain dispersants that help maintainthe cleanliness of the oil. However, dispersants were not alwaysincluded in automotive gear oil products. With the tendency towards moresynthetics, there is a need to provide improved cleanliness to some ofthe older automotive gear oil formulations, without losing theperformance that the automotive gear oil provided. Unfortunately, it hasbeen found that the addition of dispersant to an automotive gear oil canhave a detrimental effect on the frictional characteristics of the oil.As frictional characteristics are a set parameter for a given oil, asolution is needed to balance the need for cleanliness while maintainingproper friction.

SUMMARY OF THE INVENTION

The present technology solves the problem of balancing cleanliness withfrictional properties in automotive gear oils by providing an automotivegear oil for lubricating an automotive gear having an oil of lubricatingviscosity, 1 wt % or less of a dispersant, and at least one boroncontaining compound in an amount sufficient to provide from about 75 ppmto about 500 ppm of boron to the automotive gear oil.

It has been found that the presence of the boron-containing compound notonly enhances the cleansing ability of any dispersant present, but alsosuppresses any harmful effects to the oil's frictional characteristicsfrom the dispersant.

In an embodiment, the dispersant in the automotive gear oil can be asuccinimide dispersant.

In an embodiment, the at least one boron-containing compound can be aborate ester of formula I,

-   -   wherein each R, independently, is a C₃ to C₁₂ alkyl,

In some embodiments, the borate ester can be present from about 0.2 to2.0 wt % of the automotive gear oil.

In embodiments, the automotive gear oil can also include at least onephosphorous containing compound present in an amount to deliver 100 to1500 ppm of phosphorus to the automotive gear oil. In embodiments, thephosphorous containing compound can be at least one of: (1) a C₃₋₈hydrocarbyl phosphite, (2) a phosphite ester composition that comprisesthe reaction product of a monomeric phosphorous acid or an ester thereofwith at least two alkylene diols, or (3) mixtures of (1) and (2).

The automotive gear oil can also include 0.01 wt % to 0.5 wt % of adimercaptothiadiazole or derivative thereof, and/or 0.1 wt % to 5 wt %of a poly(meth)acrylate ester polymer viscosity modifier.

In an embodiment, the automotive gear oil can have a kinematic viscosityat 100° C. of from 8 cSt to 24 cSt.

The disclosed technology also includes a method of lubricating anautomotive gear by supplying to the automotive gear the automotive gearoil composition, and operating the automotive gear. The automotive gearcan be, for example, in a manual transmission, on an axle, and/or on adifferential.

DETAILED DESCRIPTION OF THE INVENTION

Various preferred features and embodiments will be described below byway of non-limiting illustration.

One aspect of the present technology is an automotive gear oil. Theautomotive gear oil can be employed to provide lubrication to the gearsof automotive vehicles, such as, for example, manual transmissions,axles and differentials. The composition can include, among otherthings, an oil of lubricating viscosity, 1 wt % or less of a dispersant,and at least one boron-containing compound.

Oils of Lubricating Viscosity

Oils of lubricating viscosity may also be defined as specified in theAmerican Petroleum Institute (API) Base Oil InterchangeabilityGuidelines (2011). The five base oil groups are as follows: Group I(sulfur content >0.03 wt %, and/or <90 wt % saturates, viscosity index80 to less than 120); Group II (sulfur content ≤0.03 wt %, and ≥90 wt %saturates, viscosity index 80 to less than 120); Group III (sulfurcontent ≤0.03 wt %, and ≥90 wt % saturates, viscosity index ≥120); GroupIV (all polyalphaolefins (PAOs)); and Group V (all others not includedin Groups I, II, III, or IV). The oil of lubricating viscosity may alsobe a Group II+ base oil, which is an unofficial API category that refersto a Group II base oil having a viscosity index greater than or equal to110 and less than 120, as described in SAE publication “Design Practice:Passenger Car Automatic Transmissions,” fourth Edition, AE-29, 2012,page 12-9, as well as in U.S. Pat. No. 8,216,448, column 1 line 57. Theoil of lubricating viscosity may also be a Group III+ base oil, which,again, is an unofficial API category that refers to a Group III base oilhaving a viscosity index of greater than 130, for example 130 to 133 oreven greater than 135, such as 135-145. Gas to liquid (“GTL”) oils aresometimes considered Group III+ base oils.

The oil of lubricating viscosity may be an API Group IV oil, or mixturesthereof, i.e., a polyalphaolefin. The polyalphaolefin may be prepared bymetallocene catalyzed processes or from a non-metallocene process. Theoil of lubricating viscosity may also comprise an API Group I, Group II,Group III, Group IV, Group V oil or mixtures thereof. Often the oil oflubricating viscosity is an API Group I, Group II, Group II+, Group III,Group IV oil or mixtures thereof. Alternatively the oil of lubricatingviscosity is often an API Group II, Group II+, Group III or Group IV oilor mixtures thereof. Alternatively the oil of lubricating viscosity isoften an API Group II, Group II+, Group III oil or mixtures thereof.

The oil of lubricating viscosity, or base oil, will overall have akinematic viscosity at 100° C. of 2 to 10 cSt or, in some embodiments2.25 to 9 or 2.5 to 6 or 7 or 8 cSt, as measured by ASTM D445. Kinematicviscosities for the base oil at 100° C. of from about 3.5 to 6 or from 6to 8 cSt are also suitable.

The amount of the oil of lubricating viscosity present is typically thebalance remaining after subtracting from 100 wt % the sum of the amountof the performance additives in the composition. Illustrative amountsmay include 50 to 99 percent by weight, or 60 to 98, or 70 to 95, or 80to 94, or 85 to 93 percent.

The lubricating composition may be in the form of a concentrate and/or afully formulated lubricant. If the lubricating composition of theinvention is in the form of a concentrate (which may be combined withadditional oil to form, in whole or in part, a finished lubricant), theratio of the components of the invention to the oil of lubricatingviscosity and/or to diluent oil include the ranges of 1:99 to 99:1 byweight, or 80:20 to 10:90 by weight.

Dispersant

The automotive gear oil will contain 1 wt % or less of a dispersant.Many types of dispersants are known in the art.

“Carboxylic dispersants” are reaction products of carboxylic acylatingagents (acids, anhydrides, esters, etc.) containing at least about 34and preferably at least about 54 carbon atoms with nitrogen containingcompounds (such as amines), organic hydroxy compounds (such as aliphaticcompounds including monohydric and polyhydric alcohols, or aromaticcompounds including phenols and naphthols), and/or basic inorganicmaterials. These reaction products include imide, amide, and esterreaction products of carboxylic ester dispersants.

The carboxylic acylating agents include fatty acides, isoaliphatic acids(e.g. 8-methyl-octadecanoic acid), dimer acids, addition dicarboxylicacids (addition (4+2) and 2+2) products of an unsaturated fatty acidwith an unsaturated carboxylic reagent), trimer acids, additiontricarboxylic acids (Empol® 1040, Hystrene® 5460 and Unidyme® 60), andhydrocarbyl substituted carboxylic acylating agents (from olefins and/orpolyalkenes). In one embodiment, the carboxylic acylating agent is afatty acid. Fatty acids generally contain from about 8 up to about 30,or from about 12 up to about 24 carbon atoms. Carboxylic acylatingagents are taught in U.S. Pat. Nos. 2,444,328, 3,219,666 and 4,234,435,the disclosures of which is hereby incorporated by reference.

The amine may be a mono- or polyamine. The monoamines generally have atleast one hydrocarbyl group containing from 1 to about 24 carbon atoms,or from 1 to about 12 carbon atoms. Examples of monoamines include fatty(C8-30) amines (Armeens), primary ether amines (SURFAM® amines),tertiary-aliphatic primary amines (“Primenes”), hydroxyamines (primary,secondary or tertiary alkanol amines), ether N-(hydroxyhydrocarbyl)amines, and hydroxyhydrocarbyl amines (“Ethomeens” and “Propomeens). Thepolyamines include alkoxylated diamines (Ethoduomeens), fatty diamines(“Duomeens”), alkylenepolyamines (ethylenepoly-amines),hydroxy-containing polyamines, polyoxyalkylene polyamines (Jeffamines),condensed polyamines (a condensation reaction between at least onehydroxy compound with at least one polyamine reactant containing atleast one primary or secondary amino group), and heterocyclicpolyamines. Useful amines include those disclosed in U.S. Pat. No.4,234,435 (Meinhart) and U.S. Pat. No. 5,230,714 (Steckel) which areincorporated herein by reference.

An example carboxylic dispersant can include, for example, “succinimidedispersants,” prepared by the reaction of a hydrocarbyl-substitutedsuccinic acylating agent with an amine such as a polyamine.

The hydrocarbyl-substituted succinic acylating agents include succinicacids, halides, esters, and anhydrides, preferably, acids, esters oranhydrides, more preferably anhydrides. The hydrocarbyl group generallycontains an average of at least about 8, or about 30, or about 35 up toabout 350, or to about 200, or to about 100 carbon atoms. In oneembodiment, the hydrocarbyl group is derived from a polyalkene, such as,for example, polyisobutylene, generally having a number averagemolecular weight of from 100 to 5000, or 500 to 4000 or 1000 to 3000.

The amine which reacts with the succinic acylating agent may be apolyamine. The polyamine may be aliphatic, cycloaliphatic, heterocyclicor aromatic. Examples of the polyamines include alkylene polyamines,hydroxy containing polyamines, arylpolyamines, and heterocyclicpolyamines.

“Amine dispersants” are reaction products of relatively high molecularweight aliphatic halides and amines, preferably polyalkylene polyamines.

“Mannich dispersants” are the reaction products of alkyl phenols inwhich the alkyl group contains at least about 30 carbon atoms withaldehydes (especially formaldehyde) and amines (especially polyalkylenepolyamines).

Post-treated dispersants are obtained by reacting carboxylic, amine orMannich dispersants with reagents such as dimercaptothiadiazoles, urea,thiourea, carbon disulfide, aldehydes, ketones, carboxylic acids,hydrocarbon-substituted succinic anhydrides, nitriles, epoxides, boroncompounds, phosphorus compounds or the like.

Polymeric dispersants are interpolymers of oil-solubilizing monomerssuch as decyl methacrylate, vinyl decyl ether and high molecular weightolefins with monomers containing polar substituents, e.g., aminoalkylacrylates or acrylamides and poly-(oxyethylene)-substituted acrylates.

Dispersants and dispersant chemistry is well-known in the art. Thedispersants suitable for use in the automotive gear oils describedherein are not particularly limited. Rather, the level of dispersant maybe minimized in view of the use of the boron-containing compounds, asdescribed below.

Mixtures of the foregoing dispersants can also be used. The dispersantcan have a nitrogen content of greater than or equal to about 11,000 ppmby weight of the dispersant, or greater than or equal to about 11,500ppm or greater than or equal to about 12,000 ppm.

The total amount of dispersant or dispersants, whether post-treated ornot (e.g., borated or non-borated) or combinations thereof, in thecompositions, may be, for instance, 0.01 to 1 percent by weight, or, forexample, 0.025 to 0.9 percent or 0.05 to 0.8 weight percent of the finalblended fluid formulation, although in a concentrate, the amounts willbe proportionately higher. In an embodiment, the automotive gear oil maybe substantially free of the above-described dispersant, or evencompletely free of the above described dispersant.

Boron-Containing Compound

The automotive gear oil can contain a boron-containing compound in anamount sufficient to provide from about 75 ppm to about 500 ppm of boronto the automotive gear oil, or from about 85 to about 450 ppm or about95 to about 350 ppm boron, or from about 100 to about 400 ppm boron tothe automotive gear oil.

The boron can be delivered by many types of boron-containing compounds.The boron can, for example, come from a borated dispersant.

The boron-containing compound can include boron containing frictionmodifiers, such as, for example, borated fatty epoxides, boratedglycerol esters, and borated alkoxylated fatty amines.

The boron containing compound can also include borated detergents. Theborated detergents can include, for example, overbased boratedmaterials, which are described in U.S. Pat. Nos. 5,403,501 and4,792,410.

The boron containing compound can also include a borate ester. Theborate ester may be a compound represented by one or more of theformulae:

wherein each R can be, independently a hydrocarbyl group, as that termis defined herein, and any two adjacent R groups may together form acyclic group. Mixtures of two or more of the foregoing may be used. Thetotal number of carbon atoms in the R groups in each formula should besufficient to render the compound soluble in the oil of lubricatingviscosity. Generally, the total number of carbon atoms in the R groupsis at least about 3, and in one embodiment at least about 5, and in oneembodiment at least about 8. There is no limit to the total number ofcarbon atoms in the R groups that is required, but a practical upperlimit is about 400 or about 500 carbon atoms.

In embodiments, each R can independently be a hydrocarbyl groupcontaining 1 to 14, or from 2 to 13 or even 3 to 10 or 12 carbon atoms,provided the sum total number of carbon atoms in all R is 3 or more,preferably 4 or more and even more preferably 6 or more. In someembodiments, each R, independently, can be a C₃ to C₂₂, or C₃ to C₁₈, orC₃ to C₁₂ alkyl. Examples of useful R groups include isopropyl, n-butyl,isobutyl, amyl, 4-methyl-2-pentyl, 2-ethyl-1-hexyl, isooctyl, decyl,dodecyl, 2-propylheptyl, tetradecyl, 2-pentenyl, dodecenyl, phenyl,naphthyl, alkylphenyl, and the like. Others can be found, for example,in WO2017/083548.

Suitable examples of the borate ester include, for example, tripropylborate, tributyl borate, tripentyl borate, trihexyl borate, triheptylborate, trioctyl borate, trinonyl borate and tridecyl borate. Otherborate ester examples can include, for example, the compound of formulaI, wherein each R is, independently, a C₃ to C₂₂, or C₃ to C₁₈, or C₃ toC₁₂ alkyl, such as, for example, tri-2-ethylhexyl borate,tris(2-propylheptyl) borate and mixtures thereof. In an embodiment theborate ester can be a C₈ borate ester, or a C₁₀ borate ester. In oneembodiment the borate ester can be tris(2-propylheptyl) borate. In someembodiments the borate ester can be tri-2-ethylhexyl borate.

In one embodiment, the borated ester can be represented by the formulaB(OC₅H₁₁)₃ or B(OC₄H₉)₃. In one embodiment, the borated ester can betri-n-butyl borate.

In one embodiment, the borated ester can be a phenolic compoundrepresented by the formula

wherein in formula VII: R₁, R₂, R₃ and R₄ are independently hydrocarbylgroups of 1 to about 12 carbon atoms; and R₅ and R₆ are independentlyalkylene groups of 1 to about 6 carbon atoms, and in one embodimentabout 2 to about 4 carbon atoms, and in one embodiment about 2 or about3 carbon atoms. In one embodiment, R₁ and R₂ independently contain 1 toabout 6 carbon atoms, and in one embodiment each is a t-butyl group. Inone embodiment, R₃ and R₄ are independently hydrocarbyl groups of about2 to about 12 carbon atoms, and in one embodiment about 8 to about 10carbon atoms. In one embodiment, R₅ and R₆ are independently —CH₂CH₂— or—CH₂CH₂CH₂—.

In one embodiment, the borated ester can be a compound represented bythe formula:

wherein in formula IX, each R is independently hydrogen or a hydrocarbylgroup. Each of the hydrocarbyl groups may contain from 1 to about 12carbon atoms, and in one embodiment 1 to about 4 carbon atoms. Anexample is 2,2′-oxy-bis-(4,4,6-trimethyl-1,3,2-dioxaborinane).

The borate ester may be employed in the automotive gear oil at about 0.2or 0.3 to about 2.0 wt. % based on the weight of the automotive gearoil, or in some cases about 0.35 to 2.0 wt. %, and in one embodimentfrom about 0.25 to about 1.0 wt. %, and in one embodiment about 0.25 toabout 0.75 wt. %.

Other Additives

The automotive gear oil can contain further additives aside from thedispersant and boron-containing compound.

Phosphorus Containing Compound

The automotive gear oil can additionally contain a phosphorouscontaining compound. The phosphorus-containing compound may be an acid,salt or ester. In one embodiment the phosphorus-containing compounds arein the form of a mixture of two or three, or two to four (typically twoor three) phosphorus-containing compounds.

In some embodiments the phosphorus-containing compound is a phosphite.Suitable phosphites include those having at least one hydrocarbyl groupwith 3 or 4 or more, or 8 or more, or 12 or more, carbon atoms. Thephosphite may be a mono-hydrocarbyl substituted phosphite, adi-hydrocarbyl substituted phosphite, or a tri-hydrocarbyl substitutedphosphite.

In one embodiment the phosphite is sulphur-free i.e., the phosphite isnot a thiophosphite.

The phosphite may be represented by the formulae:

wherein at least one R may be a hydrocarbyl group containing at least 3carbon atoms and the other R groups may be hydrogen. In one embodiment,two of the R groups are hydrocarbyl groups, and the third is hydrogen.In one embodiment every R group is a hydrocarbyl group, i.e., thephosphite is a tri-hydrocarbyl substituted phosphite. The hydrocarbylgroups may be alkyl, cycloalkyl, aryl, acyclic or mixtures thereof.

The R hydrocarbyl groups may be linear or branched, typically linear,and saturated or unsaturated, typically saturated.

In one embodiment, the phosphorus-containing compound can be a C₃₋₈hydrocarbyl phosphite, or mixtures thereof, i.e., wherein each R mayindependently be hydrogen or a hydrocarbyl group having 3 to 8, or 4 to6 carbon atoms, typically 4 carbon atoms. Typically the C₃₋₈ hydrocarbylphosphite comprises dibutyl phosphite. The C₃₋₈ hydrocarbyl phosphitemay deliver at least 175 ppm, or at least 200 ppm of the total amount ofphosphorus delivered by the phosphorus-containing compounds. The C₃₋₈hydrocarbyl phosphite may deliver at least 45 wt %, or 50 wt % to 100 wt%, or 50 wt % to 90 wt % or 60 wt % to 80 wt % of the total amount ofphosphorus from the phosphorus-containing compound.

In one embodiment, the phosphorus-containing compound can be a C₁₂-22hydrocarbyl phosphite, or mixtures thereof, i.e., wherein each R mayindependently be hydrogen or a hydrocarbyl group having 12 to 24, or 14to 20 carbon atoms, typically 16 to 18 carbon atoms. Typically theC₁₂₋₂₂ hydrocarbyl phosphite comprises a C₁₆₋₁₈ hydrocarbyl phosphite.Examples of alkyl groups for R³, R⁴ and R⁵ include octyl, 2-ethylhexyl,nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl,hexadecyl, heptadecyl, octadecyl, octadecenyl, nonadecyl, eicosyl ormixtures thereof. The C₁₂₋₂₂ hydrocarbyl phosphite may be present in theautomotive gear oil at about 0.05 wt. % to about 1.0 wt. % of theautomotive gear oil, or from about 0.1 wt. % to about 0.5 wt. % of theautomotive gear oil.

In some embodiments, the phosphorous containing compound can includeboth a C₃₋₈ and a C₁₂ to C₂₄ hydrocarbyl phosphite.

The lubricant composition optionally further contains an antiwear agentin the form of a hydrocarbyl amine salt of an alkyl(thio)phosphate. Thealkyl(thio)phosphate may also be an amine alkylthiophoshate, wherein thealkylthiophoshate is represented by the formula (R′O)₂PSSH, wherein eachR′ is independently a hydrocarbyl group containing from about 3 to about30, preferably from about 3 up to about 18, or from about 3 up to about12, or from up to about 8 carbon atoms. Example R′ groups can includeisopropyl, isobutyl, n-butyl, sec-butyl, the various amyl, n-hexyl,methylisobutyl carbinyl, heptyl, 2-ethylhexyl, isooctyl, nonyl, behenyl,decyl, dodecyl, and tridecyl groups. Illustrative lower alkylphenyl R′groups include butylphenyl, amylphenyl, heptylphenyl, etc. Examples ofmixtures of R′ groups include: 1-butyl and 1-octyl; 1-pentyl and2-ethyl-1-hexyl; isobutyl and n-hexyl; iso-butyl and isoamyl; 2-propyland 2-methyl-4-pentyl; isopropyl and sec-butyl; and iso-propyl andisooctyl.

In one embodiment, the alkylthiophoshate of the amine alkylthiophoshatemay be reacted with an epoxide or a polyhydric alcohol, such asglycerol. This reaction product may be used alone, or further reactedwith a phosphorus acid, anhydride, or lower ester. The epoxide isgenerally an aliphatic epoxide or a styrene oxide. Examples of usefulepoxides include ethylene oxide, propylene oxide, butene oxide, octeneoxide, dodecene oxide, styrene oxide, etc. Ethylene oxide and propyleneoxide are preferred. The polyhydric alcohols are described above. Theglycols may be aliphatic glycols having from 1 to about 12, or fromabout 2 to about 6, or from 2 or 3 carbon atoms. Glycols includeethylene glycol, propylene glycol, and the like. The alkylthiophoshate,glycols, epoxides, inorganic phosphorus reagents and methods of reactingthe same are described in U.S. Pat. Nos. 3,197,405 and 3,544,465 whichare incorporated herein by reference for their disclosure to these.

In one embodiment the hydrocarbyl amine salt of an alkyl(thio)phosphateis the reaction product of a C₁₄ to C₁₈ alkylated phosphoric acid withPrimene 81R™ (produced and sold by Rohm & Haas) which is a mixture ofC₁₁ to C₁₄ tertiary alkyl primary amines. Other amines which may be usedinclude alkyl alkanol amines, dialkanolamines, trialkanolamines such astriethanolamines as well as borated amines as described hereinbelow.

The amine salt as used as this component may thus comprise a C₈ to C₂₀alkylamine salt of a mono- or di-alkyl phosphate ester, or mixturesthereof.

The amount of the hydrocarbyl amine salt of an alkylphosphoric acidester in the lubricant can be 0.3 to 2 weight percent, or 0.4 to 1.9, or0.5 to 1.8, or 0.7 to 1.7 weight percent. The amounts will beproportionally higher in a concentrate. The amount of said amine saltmay also be an amount to contribute 0.03 to 0.2 weight percentphosphorus to the lubricant composition, or alternatively 0.08 to 0.17,or 0.11 to 0.17 weight percent.

The automotive gear oil can also include a substantially sulfur-freealkyl phosphate amine salt having at least 30 mole percent of thephosphorus atoms in an alkyl pyrophosphate structure, as opposed to anorthophosphate (or monomeric phosphate) structure. The percentage ofphosphorus atoms in the pyrophosphate structure may be 30 to 100 mole %,or 40 to 90% or 50 to 80% or 55 to 70% or 55 to 65%. The remainingamount of the phosphorus atoms may be in an orthophosphate structure ormay consist, in part, in unreacted phosphorus acid or other phosphorusspecies. In one embodiment, up to 60 or up to 50 mole percent of thephosphorus atoms are in mono- or di-alkyl-orthophosphate salt structure.

The substantially sulfur-free alkyl phosphate amine salt, as present inthe pyrophosphate form (sometimes referred to as the POP structure), maybe represented in part by the following formulas (I) and/or (II):

or variants thereof, such as:

where, each R¹ is independently an alkyl group of 3 to 12 carbon atoms,such as, for example, 2-butyl, 2-pentyl, 3-pentyl, 3-methyl-2-butyl,2-hexyl, 3-hexyl, cyclohexyl, 4-methyl-2-pentyl, and other suchsecondary groups and isomers thereof having 6, 7, 8, 9, 10, 11, or 12carbon atoms. In some embodiments the alkyl group can have a methylbranch at the α-position of the group, an example being the4-methyl-2-pentyl (also referred to as 4-methylpent-2-yl) group.

While the pyrophosphate ester may be isolated, if desired, from theortho-esters, it is also possible, and may be commercially preferable,to use the reaction mixture without separation of the components.

The structures of formulas (I) and (II) are shown as entirelysulfur-free species, in that the phosphorus atoms are bonded to oxygen,rather than sulfur atoms. However, it is possible that a small molarfraction of the 0 atoms could be replaced by S atoms, such as 0 to 5percent or 0.1 to 4 percent or 0.2 to 3 percent or 0.5 to 2 percent.

The pyrophosphate phosphate ester or mixture of phosphate esters with bereacted with an amine to form an amine salt. The extent ofneutralization in practice, that is, the degree of salting of the —OHgroups of the phosphorus esters, may be 50% to 100%, or 80% to 99%, or90% to 98%, or 93% to 97%, or about 95%, which may be determined orcalculated on the basis of the amount of amine charged to the phosphateester mixture.

The amine may be represented by R² ₃N, where each R² is independentlyhydrogen or a hydrocarbyl group or an ester-containing group, or anether-containing group, provided that at least one R² group is ahydrocarbyl group or an ester-containing group or an ether-containinggroup (that is, not NH₃). Suitable hydrocarbyl amines include primary,secondary or tertiary amines having 1 to 18 carbon atoms, or 3 to 12, or4 to 10 carbon atoms. Ester containing amines, such as anN-hydrocarbyl-substituted γ- or δ-amino(thio)ester. The amine, ofwhatever type, will be reacted to neutralize the acidic group(s) on thephosphorus ester component, which will comprise the pyrophosphate esteras described above as well as any orthophosphate esters that may bepresent.

The amount of the substantially sulfur-free alkyl phosphate amine saltin the lubricant composition may be 0.1 to 5 percent by weight. Thisamount refers to the total amount of the phosphate amine salt or salts,of whatever structure, both orthophosphate and pyrophosphate (with theunderstanding that at least 30 mole percent of the phosphorus atoms arein an alkyl pyrophosphate salt structure). The amounts of the phosphateamine salts in the pyrophosphate structure may be readily calculatedtherefrom. Alternative amounts of the alkyl phosphate amine salt may be0.2 to 3 percent, or 0.2 to 1.2 percent, or 0.5 to 2 percent, or or 0.6to 1.7 percent, or 0.6 to 1.5 percent, or 0.7 to 1.2 percent by weight.The amount may be suitable to provide phosphorus to the lubricantformulation in an amount of 200 to 3000 parts per million by weight(ppm), or 400 to 2000 ppm, or 600 to 1500 ppm, or 700 to 1100 ppm, or1100 to 1800 ppm.

The automotive gear oil can also include a material represented by theformula

wherein R¹ and R² are each independently hydrocarbyl groups of 3 to 12carbon atoms, or 6 to 8 carbon atoms, or are groups represented by

or wherein R¹ and R² together with the adjacent 0 and P atoms form aring containing 2 to 6 carbon atoms; R³ is hydrogen or a methyl group,R⁴ is an alkylene group of 2 to 6 carbon atoms, R⁵ is hydrogen or ahydrocarbyl group of 1 to about 12 carbon atoms, and n is 1 or 2. Thematerial represented by the above formula is typically a neutralcompound (or mixture of compounds) as the hydrogen atom shown attachedto the phosphorus is not considered to be particularly acidic.

In certain embodiments the material of Formula X may be represented bythe formula

that is, Formula X in which R³ is hydrogen, R⁴ is an ethylene group, andn is 2. As in the case of Formula X, one or both of the R¹ or R² groupsmay groups represented by

In either Formula X or Formula XI, in certain embodiments R¹ and R² mayeach independently be C₆ or C₈ alkyl groups, or mixtures thereof, suchas 2-ethylhexyl groups or 4-methyl-2-pentyl groups or mixtures thereof.

The amount of any the phosphorous ester product described above used inthe automotive gear oil may be an amount sufficient to provide 0.01 to0.3 or to 0.1 weight percent phosphorus to the composition or, in otherembodiments, 0.02 to 0.07 weight percent or 0.025 to 0.05 weightpercent. The actual amount of the product which corresponds to theseamounts of phosphorus will, of course, depend upon its phosphoruscontent. Suitable amounts of the ester product in the automotive gearoil may be 0.01 to 1.0 weight percent, or 0.02 to 0.5 weight percent, or0.03 to 0.30 weight percent, or even 0.05 to 0.25 weight percent.

While each of the phosphorus containing compounds described above may bepresent in the automotive gear oil on its own, the automotive gear oilmay also include a mixture of two or more. In some embodiments, thephosphorous containing compound can include a C₃₋₈ hydrocarbyl phosphiteand a phosphite ester product. In some embodiments, the phosphorouscontaining compound can include each of a C₃₋₈ hydrocarbyl phosphite, aC₁₂ to C₂₄ hydrocarbyl phosphite, and a phosphite ester product. Ineither event, the phosphorus containing compound should be present in anamount to deliver 100 to 1500 ppm of phosphorus to the automotive gearoil. In some embodiments, the at least one phosphorus containingcompound can be present in an amount to deliver 250 to 1250 ppm ofphosphorus, or from 500 to 1000 ppm phosphorus to the automotive gearoil.

Another component of the automotive gear oil can be a metal deactivator.Examples of such materials include 2,5-dimercapto-1,3,4-thiadiazoleand/or derivatives thereof. Such materials are described in EuropeanPatent Publication 0761805, incorporated herein by reference. Furtherexamples of the metal deactivator include the thiadiazole compounds,such as those described in U.S. Pat. No. 9,816,044, and represented bythe formula:

The metal deactivators that are useful herein reduce the corrosion ofmetals, such as copper. Metal deactivators are also referred to as metalpassivators. These metal deactivators are typically nitrogen and/orsulfur containing heterocyclic compounds, such asdimercaptothiadiazoles, triazoles, aminomercaptothiadiazoles,imidazoles, thiazoles, tetrazoles, hydroxyquinolines, oxazolines,imidazolines, thiophenes, indoles, indazoles, quinolines, benzoxazines,dithiols, oxazoles, oxatriazoles, pyridines, piperazines, triazines, andderivatives of any one or more thereof. The metal deactivator preferablycomprises at least one triazole, which may be substituted orunsubstituted. Examples of suitable compounds are benzotriazole,alkyl-substituted benzotriazole (e.g., tolyltriazole,ethylbenzotriazole, hexylbenzotriazole, octylbenzotriazole, etc.),aryl-substituted benzotriazole (e.g., phenol benzotriazoles, etc.), andalkylaryl- or arylalkyl-substituted benzotriazole and substitutedbenzotriazoles where the substituent may be hydroxy, alkoxy, halo(especially chloro), nitro, carboxy and carboxyalkoxy. Preferably, thetriazole is a benzotriazole or an alkylbenzotriazole in which the alkylgroup contains 1 to about 20 carbon atoms, preferably 1 to about 8carbon atoms. Benzotriazole and tolyltriazole are useful.

In one embodiment, the metal deactivator is the reaction product of adispersant with a dimercaptothiadiazole. The dispersants may begenerally characterized as the reaction products of carboxylic acidswith amines and/or alcohols. These reaction products are commonly usedin the lubricant arts as dispersants and are sometimes referred togenerically as dispersants despite the fact that they may have otheruses in addition to or instead of that as dispersants. The carboxylicdispersants include succinimide dispersants, ester type dispersants andthe like. Succinimide dispersants are generally the reaction of apolyamine with an alkenyl succinic anhydride or acid. Ester typedispersants are the reaction product of an alkenyl succinic anhydride oracid with a polyol compound. The reaction product may then be furthertreated with an amine such as a polyamine. Examples of usefuldispersants are disclosed in U.S. Pat. Nos. 3,219,666 and 4,234,435,incorporated herein by reference. Useful dispersants also include theashless dispersants discussed below. Generally the reaction occursbetween the dispersant and the dimercaptothiadiazole by mixing the twoand heating to a temperature above about 100° C. U.S. Pat. Nos.4,140,643 and 4,136,043 describe compounds made by the reaction of suchdispersants with a dimercaptothiadiazole. These patents are incorporatedherein by reference for their disclosure of dispersants,dimercaptothiadiazole, the method for reacting the two and the productsobtained from such reaction.

In one embodiment, the metal deactivator is the reaction product of aphenol with an aldehyde and a dimercaptothiadiazole. The phenol ispreferably an alkyl phenol wherein the alkyl group contains at leastabout 6, preferably from 6 to about 24, more preferably about 6, orabout 7, to about 12 carbon atoms. The aldehyde is preferably analdehyde containing from 1 to about 7 carbon atoms or an aldehydesynthon, such as formaldehyde. Preferably, the aldehyde is formaldehydeor paraformaldehyde. The aldehyde, phenol and dimercaptothiadiazole aretypically reacted by mixing them at a temperature up to about 150° C.,preferably about 50° C. to about 130° C., in molar ratios of about 0.5to about 2 moles of phenol and about 0.5 to about 2 moles of aldehydeper mole of dimercaptothiadiazole. Preferably, the three reagents arereacted in equal molar amounts.

In one embodiment, the metal deactivator is abis(hydrocarbyldithio)thiadiazole. Preferably each hydrocarbyl group isindependently an alkyl, aryl or aralkyl group, having from 6 to about 24carbon atoms. Each hydrocarbyl can be independently t-octyl, nonyl,decyl, dodecyl or ethylhexyl. The metal deactivator can bebis-2,5-tert-octyl-dithio-1,3,4-thiadiazole or a mixture thereof with2-tert-octylthio-5-mercapto-1,3,4-thiadiazole. These materials areavailable commercially under the trade name of Amoco 150, which isavailable from Amoco Chemical Company. These dithiothiadiazole compoundsare disclosed as Component (d) in PCT Publication WO 88/03551,incorporated by reference for its disclosure of dithiothiadiazolecompounds. In the preferred embodiments the metal deactivator is adimercaptothiadiazole derivative. Example D-1 is a specific example.

Example D-1

2,5-dimercapto-1,3,4-thiadiazole oxidatively coupled with t-nonylmercaptan; 100% chemical, 36% S, 6.4% N.

When used, the amount of metal deactivator in the automotive gear oil isgenerally in the range of about 0.01 to about 0.5 wt. % by weight of theautomotive gear oil. In some embodiments, the amount of the metaldeactivator is in the range of about 0.02 to about 0.42 wt. % or about0.03 to about 0.33 wt. % or about 0.04 to about 0.24 wt. % by weight ofthe automotive gear oil.

Another material which may optionally be present is a viscositymodifier. Viscosity modifiers (VM) and dispersant viscosity modifiers(DVM) are well known. Examples of VMs and DVMs may includepolymethacrylates, polyacrylates, polyolefins, hydrogenated vinylaromatic-diene copolymers (e.g., styrene-butadiene, styreneisoprene),styrene-maleic ester copolymers, and similar polymeric substancesincluding homopolymers, copolymers, and graft copolymers, includingpolymers having linear, branched, or star-like structures. The DVM maycomprise a nitrogen-containing methacrylate polymer ornitrogen-containing olefin polymer, for example, a nitrogen-containingmethacrylate polymer derived from methyl methacrylate anddimethylaminopropyl amine. The DVM may alternatively comprise acopolymer with units derived from an α-olefin and units derived from acarboxylic acid or anhydride, such as maleic anhydride, in partesterified with a branched primary alcohol and in part reacted with anamine-containing compound.

Examples of commercially available VMs, DVMs and their chemical typesmay include the following: polyisobutylenes (such as Indopol™ from BPAmoco or Parapol™ from ExxonMobil); olefin copolymers (such as Lubrizol®7060, 7065, and 7067, and Lucant® HC-2000, HC-1100, and HC-600 fromLubrizol); hydrogenated styrene-diene copolymers (such as Shellvis™ 40and 50, from Shell and LZ® 7308, and 7318 from Lubrizol);styrene/maleate copolymers, which are dispersant copolymers (such as LZ®3702 and 3715 from Lubrizol); polymethacrylates, some of which havedispersant properties (such as those in the Viscoplex™ series fromRohMax, the Hitec™ series of viscosity index improvers from Afton, andLZ® 7702, LZ® 7727, LZ® 7725 and LZ® 7720C from Lubrizol);olefin-graft-polymethacrylate polymers (such as Viscoplex™ 2-500 and2-600 from RohMax); and hydrogenated polyisoprene star polymers (such asShellvis™ 200 and 260, from Shell). Viscosity modifiers that may be usedare described in U.S. Pat. Nos. 5,157,088, 5,256,752 and 5,395,539. TheVMs and/or DVMs may be used in the functional fluid at a concentrationof up to 50% or to 20% by weight, depending on the application.Concentrations of 1 to 20%, or 1 to 12%, or 3 to 10%, or alternatively20 to 40%, or 20 to 30% by weight may be used.

Other optional materials may include antioxidants, e.g., aromatic amineantioxidants, hindered phenolic antioxidants including ester-containinghindered phenolic antioxidants, and sulfurized olefin antioxidants. Inan embodiment, the automotive gear oil may contain a mixture of at leasttwo anti-oxidants. These antioxidants may optionally be present inamounts of 0.01 to 5, or 0.15 to 4.5 or 0.2 to 4, or 0.2 to 2 percent byweight.

In one embodiment, the automotive gear oil can include an aryl amineantioxidant. The aryl amine antioxidant may be a phenyl-α-naphthylamine(PANA) or a hydrocarbyl substituted diphenylamine, or mixtures thereof.The hydrocarbyl substituted diphenylamine may include mono- or di-C₄ toC₁₆-, or C₆ to C₁₂-, or C₉-alkyl diphenylamine. For example thehydrocarbyl substituted diphenylamine may be octyl diphenylamine, ordi-octyl diphenylamine, dinonyl diphenylamine, typically dinonyldiphenylamine.

When present the aryl amine antioxidant may be present at 0.2 wt % to1.2 wt %, or 0.3 wt % to 1.0 wt %, or 0.4 wt % to 0.9 wt % or 0.5 wt %to 0.8 wt %, of the automotive gear oil.

The hindered phenol antioxidant often contains a secondary butyl and/ora tertiary butyl group as a sterically hindering group. The phenol groupis often further substituted with a hydrocarbyl group and/or a bridginggroup linking to a second aromatic group. Examples of suitable hinderedphenol antioxidants include 2,6-ditert-butylphenol,4-methyl-2,6-di-tert-butylphenol, 4-ethyl-2,6-di-tert-butylphenol,4-propyl-2,6-di-tert-butylphenol or 4-butyl-2,6-di-tert-butylphenol, or4-dodecyl-2,6-di-tert-butylphenol. In one embodiment the hindered phenolantioxidant may be an ester and may include, e.g., Irganox™ L-135 fromCiba, or butyl 3-(3,5-di-tertbutyl-4-hydroxyphenyl)propanoate.

If present, the hindered phenol antioxidant may be present at 0.1 wt %to 1 wt %, or 0.2 wt % to 0.9 wt % or 0.1 wt % to 0.4 wt %, or 0.4 wt %to 1.0 wt %, of the automotive gear oil.

Antioxidants also include sulfurized olefins such as mono-, ordisulfides or mixtures thereof. These materials generally have sulfidelinkages having 1 to 10 sulfur atoms, for instance, 1 to 4, or 1 or 2.Materials which can be sulfurized to employ as sulfurized antioxidantsin the automotive gear oil can include oils, fatty acids and esters,olefins and polyolefins made thereof, terpenes, or Diels-Alder adducts.Details of methods of preparing some such sulfurized materials can befound in U.S. Pat. Nos. 3,471,404 and 4,191,659.

The automotive gear oil may also include a calcium-containing detergent.While the calcium-containing detergent is preferably not present, it canbe included in an amount to deliver up to 150 ppm or 180 ppm of calciumto the composition, or from 30 ppm to 180 ppm, or 30 ppm to 150 ppm ofcalcium, or from 60 ppm to 180 ppm, or even from 60 ppm to 150 ppm ofcalcium.

In some embodiments, the calcium-containing detergent may be present at90 ppm or less, or from 1 to 90 ppm, or even from 5 to 80 ppm or 10 to75 ppm.

The calcium-containing detergent may be an overbased detergent, anon-overbased detergent, or mixtures thereof. Typically the detergent isoverbased.

The preparation of the calcium-containing detergent is known in the art.Patents describing the preparation of overbased calcium-containingdetergents include U.S. Pat. Nos. 2,501,731; 2,616,905; 2,616,911;2,616,925; 2,777,874; 3,256,186; 3,384,585; 3,365,396; 3,320,162;3,318,809; 3,488,284; and 3,629,109.

The calcium-containing detergent may be a non-overbased detergent (mayalso be referred to as a neutral detergent). The TBN of a non-overbasedmay be 20 to less than 200, or 30 to 100, or 35 to 50 mg KOH/g. The TBNof a non-overbased calcium-containing detergent may also be 20 to 175,or 30 to 100 mg KOH/g. When a non-overbased calcium-containing detergentis prepared from a strong acid such as a hydrocarbyl-substitutedsulphonic acid, the TBN may be lower (for example 0 to 50 mg KOH/g, or10 to 20 mg KOH/g).

As used herein the TBN values quoted and associated range of TBN is on“an as is basis,” i.e., containing conventional amounts of diluent oil.Conventional amounts of diluent oil typically range from 30 wt % to 60wt % (often 40 wt % to 55 wt %) of the detergent component.

The calcium-containing detergent may be an overbased detergent, having,for example, a TBN of greater than 200 mg KOH/g (typically 250 to 600,or 300 to 500 mg KOH/g).

The overbased calcium-containing detergent may be formed by the reactionof a basic calcium compound and an acidic detergent substrate. Theacidic detergent substrate may include an alkyl aromatic sulphonic acid(such as, alkyl naphthalene sulphonic acid, alkyl toluene sulphonic acidor alkyl benzene sulphonic acid), an alkyl salicylic acid, or mixturesthereof.

The basic calcium compound is used to supply basicity to the detergent.The basic calcium compound is a compound of a hydroxide or oxide of thecalcium.

The oxides and/or hydroxides may be used alone or in combination. Theoxides or hydroxides may be hydrated or dehydrated, although hydrated istypical. In one embodiment the basic calcium compound may be calciumhydroxide, which may be used alone or mixtures thereof with other metalbasic compounds. Calcium hydroxide is often referred to as lime. In oneembodiment the calcium basic compound may be calcium oxide which may beused alone or mixtures thereof with other metal basic compounds.

In one embodiment the calcium-containing detergent may be a sulphonate,or mixtures thereof. The sulphonate may be prepared from a mono- ordi-hydrocarbyl-substituted benzene (or naphthalene, indenyl, indanyl, orbicyclopentadienyl) sulphonic acid, wherein the hydrocarbyl group maycontain 6 to 40, or 8 to 35 or 9 to 30 carbon atoms.

The hydrocarbyl group may be derived from polypropylene or a linear orbranched alkyl group containing at least 10 carbon atoms. Examples of asuitable alkyl group include branched and/or linear decyl, undecyl,dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl,octadecyl, octadecenyl, nonodecyl, eicosyl, un-eicosyl, do-eicosyl,tri-eicosyl, tetra-eicosyl, penta-eicosyl, hexa-eicosyl or mixturesthereof.

In one embodiment the hydrocarbyl-substituted sulphonic acid may includepolypropene benzenesulphonic acid and/or C₁₆-C₂₄ alkyl benzenesulphonicacid, or mixtures thereof.

In one embodiment a calcium sulphonate detergent may be a predominantlylinear alkylbenzene sulphonate detergent having a metal ratio of atleast 8 as is described in paragraphs [0026] to [0037] of US PatentApplication 2005065045 (and granted as U.S. Pat. No. 7,407,919). In someembodiments the linear alkyl group may be attached to the benzene ringanywhere along the linear chain of the alkyl group, but often in the 2,3 or 4 position of the linear chain, and in some instances predominantlyin the 2 position.

When neutral or slightly basic, a calcium sulphonate detergent may haveTBN of less than 100, or less than 75, typically 20 to 50 mg KOH/g, or 0to 20 mg KOH/g.

When overbased, a calcium sulphonate detergent may have a TBN greaterthan 200, or 300 to 550, or 350 to 450 mg KOH/g.

Phenate detergents are typically derived from p-hydrocarbyl phenols or,generally, alkylpheols. Alkylphenols of this type may be coupled withsulfur and overbased, coupled with aldehyde and overbased, orcarboxylated to form salicylate detergents. Suitable alkylsalicylatesinclude those alkylated with oligomers of propylene, oligomers ofbutene, especially tetramers and pentamers of n-butenes, as well asthose alkylated with alpha-olefins, isomerized alpha-olefins, andpolyolefins like polyisobutylene. In one embodiment, the automotive gearoil comprises less than 0.2 wt %, or less than 0.1 wt %, or even lessthan 0.05 wt % of a salicylate detergent derived from para-dodecylphenol(PDDP). In one embodiment, the automotive gear oil comprises asalicylate detergent that is not derived from PDDP. In one embodiment,the automotive gear oil can comprise a salicylate detergent preparedfrom PDDP, such detergent contains less than 1.0 weight percentunreacted PDDP, or less than 0.5 weight percent unreacted PDDP, or issubstantially free of PDDP.

The detergent may be borated or non-borated.

Chemical structures for sulphonates, and salicylate detergents are knownto a person skilled in the art. The standard textbook entitled“Chemistry and Technology of Lubricants”, Third Edition, Edited by R. M.Mortier and S. T. Orszulik, Copyright 2010, pages 220 to 223 under thesub-heading 7.2.6 provide general disclosures of said detergents andtheir structures.

In one embodiment the calcium-containing detergent may be an overbasedcalcium sulphonate, an overbased calcium salicylate, or mixturesthereof. Typically the detergent may be an overbased calcium sulphonate.

In one embodiment the calcium-containing detergent may be in a mixturewith a zinc-, barium-, sodium-, or magnesium-containing detergent. Thezinc-, barium-, sodium-, or magnesium-containing detergent is also wellknown in the art and described in the same references describing acalcium-containing detergent. The TBN and metal ratios may however,differ slightly. The zinc-, barium-, sodium-, or magnesium-containingdetergent may be a phenate, a sulphur-containing phenate, sulphonate,salixarate or salicylate. Typically a zinc-, barium-, sodium-, ormagnesium-containing detergent may be a magnesium phenate, a magnesiumsulphur-containing phenate, or a magnesium sulphonate.

A more detailed description of the expressions “metal ratio”, TBN and“soap content” are known to a person skilled in the art and explained instandard textbooks, such as, for example, “Chemistry and Technology ofLubricants”, Third Edition, Edited by R. M. Mortier and S. T. Orszulik,Copyright 2010, pages 219 to 220 under the sub-heading 7.2.5. DetergentClassification.

The automotive gear may also include a friction modifier. In oneembodiment the friction modifier may be, for example, long chain fattyacid derivatives of amines, long chain fatty esters, or derivatives of along chain fatty epoxides; fatty imidazolines; amine salts ofalkylphosphoric acids; fatty alkyl tartrates; fatty alkyl tartrimides;fatty alkyl tartramides; fatty glycolates; and fatty glycolamides, orcombinations thereof. The friction modifier may be present at 0 wt % to6 or to 5 wt %, or 0.01 wt % to 4 wt %, or 0.05 wt % to 2 wt %, or 0.1wt % to 2 wt % of the lubricating composition. The amount of frictionmodifier, if present, also may be 0.05 to 5 percent by weight, or 0.1 to2 percent, or 0.1 to 1.5 percent by weight, or 0.15 to 1 percent, or0.15 to 0.6 percent.

As used herein the term “fatty alkyl” or “fatty” in relation to frictionmodifiers means a carbon chain having 10 to 22 carbon atoms, typically astraight carbon chain. Alternatively, the fatty alkyl may be a monobranched alkyl group, with branching typically at the β-position.Examples of mono branched alkyl groups include 2-ethylhexyl,2-propylheptyl or 2-octyldodecyl.

Examples of suitable friction modifiers include long chain fatty acidderivatives of amines, fatty esters, or fatty epoxides; fattyimidazolines such as condensation products of carboxylic acids andpolyalkylene-polyamines; amine salts of alkylphosphoric acids; fattyalkyl tartrates; fatty alkyl tartrimides; fatty alkyl tartramides; fattyphosphonates; fatty phosphites; borated phospholipids, borated fattyepoxides; glycerol esters; borated glycerol esters; fatty amines;alkoxylated fatty amines; borated alkoxylated fatty amines; hydroxyl andpolyhydroxy fatty amines including tertiary hydroxy fatty amines;hydroxy alkyl amides; metal salts of fatty acids; metal salts of alkylsalicylates; fatty oxazolines; fatty ethoxylated alcohols; condensationproducts of carboxylic acids and polyalkylene polyamines; or reactionproducts from fatty carboxylic acids with guanidine, aminoguanidine,urea, or thiourea and salts thereof.

Friction modifiers may also encompass materials such as sulphurisedfatty compounds and olefins, molybdenum dialkyldithiophosphates,molybdenum dithiocarbamates, sunflower oil or soybean oil monoester of apolyol and an aliphatic carboxylic acid.

In one embodiment the friction modifier may be a long chain fatty acidester. In another embodiment the long chain fatty acid ester may be amono-ester and in another embodiment the long chain fatty acid ester maybe a triglyceride

In an embodiment, the automotive gear oil is substantially free offriction modifiers. In some embodiments, the automotive gear oil iscompletely free of friction modifiers.

The automotive gear oil may have a kinematic viscosity at 100° C. offrom 8 cSt to 24 cSt, or for example, from 9 cSt to 21 cSt, or even 10cSt to 20 cSt.

One aspect is therefore a method of lubricating an automotive gear bysupplying to the automotive gear the automotive gear oil as disclosedherein, and operating the automotive gear. The automotive gear oil willbe suitable for lubricating automotive gears, including gears intransmissions, such as manual or dual clutch transmission, gears onaxles, and gears on differentials.

The automotive gear oil may, in particular, be employed in a manualgearbox of a manual transmission, which may be unsynchronized, or maycontain a synchronizer mechanism. The gearbox may be self-contained, ormay additionally contain any of a transfer gearbox, planetary gearsystem, differential, limited slip differential or torque vectoringdevice, which may be lubricated by a manual transmission fluid.

The automotive gear oil may be used in planetary hub reduction axles,mechanical steering and transfer gear boxes in utility vehicles,synchromesh gear boxes, power take-off gears, limited slip axles, andplanetary hub reduction gear boxes.

In an embodiment, the automotive gear oil can be employed as a singlelubricant to lubricate the entire driveline system of an automobilehaving a manual transmission. That is, in an embodiment, the automotivegear oil may be employed as a “total driveline lubricant,” suitable tolubricate all the gears in the automobile, including in the transmissionand in the axles and differentials.

As used herein, the term “condensation product” is intended to encompassesters, amides, imides and other such materials that may be prepared bya condensation reaction of an acid or a reactive equivalent of an acid(e.g., an acid halide, anhydride, or ester) with an alcohol or amine,irrespective of whether a condensation reaction is actually performed tolead directly to the product. Thus, for example, a particular ester maybe prepared by a transesterification reaction rather than directly by acondensation reaction. The resulting product is still considered acondensation product.

The amount of each chemical component described is presented exclusiveof any solvent or diluent oil, which may be customarily present in thecommercial material, that is, on an active chemical basis, unlessotherwise indicated. However, unless otherwise indicated, each chemicalor composition referred to herein should be interpreted as being acommercial grade material which may contain the isomers, by-products,derivatives, and other such materials which are normally understood tobe present in the commercial grade.

As used herein, the term “hydrocarbyl substituent” or “hydrocarbylgroup” is used in its ordinary sense, which is well-known to thoseskilled in the art. Specifically, it refers to a group having a carbonatom directly attached to the remainder of the molecule and havingpredominantly hydrocarbon character. Examples of hydrocarbyl groupsinclude:

hydrocarbon substituents, that is, aliphatic (e.g., alkyl or alkenyl),alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, and aromatic-,aliphatic-, and alicyclic-substituted aromatic substituents, as well ascyclic substituents wherein the ring is completed through anotherportion of the molecule (e.g., two substituents together form a ring);

substituted hydrocarbon substituents, that is, substituents containingnon-hydrocarbon groups which, in the context of this invention, do notalter the predominantly hydrocarbon nature of the substituent (e.g.,halo (especially chloro and fluoro), hydroxy, alkoxy, mercapto,alkylmercapto, nitro, nitroso, and sulfoxy);

hetero substituents, that is, substituents which, while having apredominantly hydrocarbon character, in the context of this invention,contain other than carbon in a ring or chain otherwise composed ofcarbon atoms and encompass substituents as pyridyl, furyl, thienyl andimidazolyl. Heteroatoms include sulfur, oxygen, and nitrogen. Ingeneral, no more than two, or no more than one, non-hydrocarbonsubstituent will be present for every ten carbon atoms in thehydrocarbyl group; alternatively, there may be no non-hydrocarbonsubstituents in the hydrocarbyl group.

It is known that some of the materials described above may interact inthe final formulation, so that the components of the final formulationmay be different from those that are initially added. For instance,metal ions (of, e.g., a detergent) can migrate to other acidic oranionic sites of other molecules. The products formed thereby, includingthe products formed upon employing the composition of the presentinvention in its intended use, may not be susceptible of easydescription. Nevertheless, all such modifications and reaction productsare included within the scope of the present invention; the presentinvention encompasses the composition prepared by admixing thecomponents described above.

As used herein, the term “about” means that a value of a given quantityis within ±20% of the stated value. In other embodiments, the value iswithin ±15% of the stated value. In other embodiments, the value iswithin ±10% of the stated value. In other embodiments, the value iswithin ±5% of the stated value. In other embodiments, the value iswithin ±2.5% of the stated value. In other embodiments, the value iswithin ±1% of the stated value.

Additionally, as used herein, the term “substantially” means that avalue of a given quantity is within ±10% of the stated value. In otherembodiments, the value is within ±5% of the stated value. In otherembodiments, the value is within ±2.5% of the stated value. In otherembodiments, the value is within ±1% of the stated value.

The invention herein is useful for lubricating an automotive gear, whichmay be better understood with reference to the following examples.

EXAMPLES

Automotive gear oils were prepared and tested for dynamic friction, μ-Vgradient, and thermal stability (to test cleanliness). The fluids can beseen in table 1 below.

Baseline Baseline Experimental Fluid 1 Fluid 2 Fluid 1 4 cSt Oil ofLubricating 70.49 71.99 70.99 Viscosity Viscosity Modifier 21 21 21Extreme Pressure Agent 3.80 3.80 3.80 Corrosion Inhibitor 0.10 0.10 0.10Borated Dispersant¹ 0.43 0.31 0.31 Non-Borated Dispersant 0.71 0.18 0.18Antiwear Agent² 1.32 1.00 1.00 Antifoam 0.01 0.01 0.01 Friction Modifier0.35 0.3 0.3 Boron Containing 1.0 Compound³ Total 100 100 100 ¹Delivers133, 95 and 95 ppm Boron to the fluids, respectively ²Delivers 1115, 845and 845 ppm Phosphorus to the fluids, respectively ³Delivers 270 ppmBoron to the fluid

The formulations were tested in a synchronizer test rig in a “durabilitytest.” This is a screening test that is customarily used to evaluatefriction and durability characteristic of a clutch synchronizer. Thetest rig typically does not simulate a full engagement of thesynchronizer components, but does measure the friction between thesynchronizer ring and the gear cone. The rig comprises a test rig bathin which the components are assembled.

An Automax® rig comprises a test rig bath in which the components areassembled. The synchronizer is attached to the test rig key on one sideof the chamber and the cone assembled onto a test rig jig on the otherside. The test conditions used are shown in the Table below. The fluidsare maintained at 80° C. with the synchronizer typically rotating at1000 rpm. In each test, there is an initial break-in phase of 100 cyclesof engagement. Thereafter, multiple cycles of engagement consist of 0.2seconds of contact followed by 5 seconds of separation, running at 1000r.p.m. at 80° C. and a load during contact of 981 N (100 kg).

Oil Temperature (° C.) 80 Speed (rpm) 1000 Load (kg) 100 (N) 980.6 OnTime (sec) 0.2 Off Time (sec) 5.0 Inertia (kg cm sec²) 2.67 CalculatedTorque (Nm) 41

The key features of the synchronizer used in this experiment aresummarized in the table below. All other parts are original equipmentmanufacturer production parts used in standard vehicles:

Phenolic Resin Synchronizer Gear Cone Angle (degrees) 7.0 Effectiveradius (mm) 62 Composition Phenolic Resin

The data from the test provides several key parameters that allow acomparison of the friction performance of the candidates. Comparisons ofthe relative durability and shift quality of the different candidatesare made based upon a number of parameters including dynamic frictionlevel assessed by the friction value during durability testing, frictiondurability assessed by the stability, and trends in average frictionvalues during the durability phase.

Shift quality is assessed by examining the performance test profileswhich show the variation of friction with rotational speed. It isdesirable to have a flat frictional profile, with a level or slightdecrease in friction at low speed providing improved synchronizerengagement and improved shift quality.

The dynamic coefficient of friction may be presented as a function ofcycle number. A quantitative representation of the performance may, beobtained by calculating the number of cycles to stability. Ideally, afluid should show stable friction throughout the duration of the test.Some fluids may, vary in friction at the start of the test, beforestabilizing to a final value after a number of cycles. Other fluids maynot stabilize at all and the friction may be still increasing ordecreasing after 10,000 cycles. One method of assessing dynamic frictionis to evaluate the mean and standard deviation of the friction valuesduring the 10,000 cycle test.

Dynamic Friction Cycle μV-AVG μV-AVG μV-AVG 1 0.116 0.112 0.113 2000.119 0.116 0.115 500 0.12 0.114 0.115 1000 0.118 0.108 0.116 2000 0.1140.105 0.116 3000 0.113 0.104 0.115 4000 0.112 0.103 0.115 5000 0.1120.102 0.115 6000 0.111 0.102 0.114 7000 0.111 0.102 0.114 8000 0.1110.102 0.114 9000 0.111 0.102 0.113 10000 0.11 0.102 0.113

In order to assess the shift-quality of an individual engagement it isnecessary to evaluate the friction versus speed relationship. Oneparameter that is useful is to assess the curvature of the speed-fictionrelationship. In order to do this a chord is drawn between the μ valuesbetween 50 to 1000 rpm. The area of the difference between the actualμ_(d) and the chord gives a value that we will refer to as the curvatureof the line. A large negative curvature value represents a poor resultand a value that is close to zero or positive, indicates a betterperformance.

Pre-Test Friction Post-Test Friction Fluid 1 Fluid 2 Fluid 3 Fluid 1Fluid 2 Fluid 3 Initial Initial Initial Final Final Final Meas- Meas-Meas- Meas- Meas- Meas- rpm urement urement urement rpm urement urementurement 50 0.119 0.112 0.116 50 0.131 0.125 0.12 75 0.121 0.114 0.117 750.129 0.122 0.121 100 0.123 0.115 0.118 100 0.126 0.118 0.123 125 0.1230.115 0.118 125 0.126 0.116 0.123 200 0.121 0.114 0.117 200 0.121 0.1120.122 300 0.12 0.113 0.117 300 0.119 0.11 0.121 500 0.118 0.111 0.115500 0.116 0.107 0.119 750 0.117 0.111 0.114 750 0.113 0.105 0.116 10000.117 0.112 0.113 1000 0.113 0.103 0.114

As can be seen in the tables, Fluid 3 shows a stabilized friction overthe test cycles.

The wear performance provided by the lubricant was also be tested. Wearmay be determined from the test rig profile described above, bymeasuring mg weight loss from the synchronizer ring at the end of thetesting. The wear readings for the fluids are provided below.

Fluid Fluid Fluid 1 2 3 (mg) (mg) (mg) Wear reading 87.9 41.4 36.4

500 ml samples of the fluids were tested for thermal stability by theJIS K2514-1 Indiana Stirring Oxidation Test at 150° C., heated for 96hours at 1,300 rpm. The results are shown in the table below. The laquerrating scale is as follows: 0=no deposit, 1=light deposit, 2=mediumdeposit and 3=heavy deposit.

Fluid 1 Fluid 2 Fluid 3 Heating Time/hours Lacquer Rating 0 0 0 24 1 148 1 1 96 3 3 2

Each of the documents referred to above is incorporated herein byreference, including any prior applications, whether or not specificallylisted above, from which priority is claimed. The mention of anydocument is not an admission that such document qualifies as prior artor constitutes the general knowledge of the skilled person in anyjurisdiction. Except in the Examples, or where otherwise explicitlyindicated, all numerical quantities in this description specifyingamounts of materials, reaction conditions, molecular weights, number ofcarbon atoms, and the like, are to be understood as modified by the word“about.” It is to be understood that the upper and lower amount, range,and ratio limits set forth herein may be independently combined.Similarly, the ranges and amounts for each element of the invention canbe used together with ranges or amounts for any of the other elements.

As used herein, the transitional term “comprising,” which is synonymouswith “including,” “containing,” or “characterized by,” is inclusive oropen-ended and does not exclude additional, un-recited elements ormethod steps. However, in each recitation of “comprising” herein, it isintended that the term also encompass, as alternative embodiments, thephrases “consisting essentially of” and “consisting of,” where“consisting of” excludes any element or step not specified and“consisting essentially of” permits the inclusion of additionalun-recited elements or steps that do not materially affect the essentialor basic and novel characteristics of the composition or method underconsideration.

While certain representative embodiments and details have been shown forthe purpose of illustrating the subject invention, it will be apparentto those skilled in this art that various changes and modifications canbe made therein without departing from the scope of the subjectinvention. In this regard, the scope of the invention is to be limitedonly by the following claims.

What is claimed is:
 1. An automotive gear oil for lubricating anautomotive gear comprising a. an oil of lubricating viscosity b. 0.025to 0.9 wt. % of a succinimide dispersant, and c. about 0.2 to 2.0 wt. %of at least one boron-containing compound in an amount sufficient toprovide from about 75 ppm to about 500 ppm of boron to the automotivegear oil, wherein that at least one boron-containing compound is aborate ester of formula I,

 wherein each R, independently, is a C₃ to C₁₂ alkyl, and d. 0.01 wt %to 0.5 wt % of a dimercaptothiadiazole or derivative thereof.
 2. Theautomotive gear oil of claim 1 wherein the automotive gear oil has akinematic viscosity at 100° C. of from 8 cSt to 24 cSt.
 3. (canceled) 4.(canceled)
 5. (canceled)
 6. The automotive gear oil of claim 1 furthercomprising at least one phosphorous containing compound present in anamount to deliver 100 to 1500 ppm of phosphorus to the automotive gearoil.
 7. The automotive gear oil of claim 6, where the phosphorouscontaining compound comprises at least one of: (1) a C₃₋₈ hydrocarbylphosphite, (2) a phosphite ester composition that comprises the reactionproduct of a monomeric phosphorous acid or an ester thereof with atleast two alkylene diols, (3) a phosphate ester amine salt, (4) apyrophosphate amine salt, or (5) mixtures of any of (1) to (4). 8.(canceled)
 9. The automotive gear oil of claim 1 further comprising aviscosity modifier.
 10. The automotive gear oil of claim 1 furthercomprising a friction modifier.
 11. The automotive gear oil of claim 1further comprising a detergent.
 12. A method of lubricating anautomotive gear comprising supplying to the automotive gear acomposition of claim 1, and operating the automotive gear.
 13. Themethod of claim 12, wherein the automotive gear is in a manualtransmission.
 14. The method of claim 12, wherein the automotive gear ison an axle.
 15. The method of claim 12, wherein the automotive gear ison a differential.